f2df4bfe54
https://github.com/llvm/llvm-project/pull/78171 added support for non-consecutive local value numbers. This extends the support for global value numbers (for globals and functions). This means that it is now possible to delete an unnamed global definition/declaration without breaking the IR. This is a lot less common than unnamed local values, but it seems like something we should support for consistency. (Unnamed globals are used a lot in Rust though.)